1193번 '분수찾기'

let input = Int(readLine()!)!
var count = 0
var flag = 1
while(input - count > flag){
    count += flag
    flag += 1
}
let remain = input - count
let sum = flag + 1
 
if(flag % 2 == 0){
    let boonza = 1
    let boonmo = flag
    print("\(boonza + remain - 1)/\(boonmo - remain + 1)")
}
else{
    let boonza = flag
    let boonmo = 1
    print("\(boonza - remain + 1)/\(boonmo + remain - 1)")
}
 
 
 

플래그를 이용해서 규칙을 잘 조작한다.